sedge
菅 refers to sedge, a type of grass-like plant often found in wetlands.
菅 combines the grass radical 艹 with 官, which likely provides the sound. The character was created to name the sedge plant.
The grass radical 艹 sits above 官, like a government official (官) inspecting a field of sedge.
For カン, imagine a can of sedge seeds being planted by an official: can -> カン.
sedge (Cyperaceae spp., esp. members of genus Carex)
softstem bulrush (Scirpus tabernaemontani)
citron daylily (Hemerocallis citrina); long yellow daylily
Carex morrowii
day lily (Hemerocallis dumortierii); orange-yellow day lily; Nikko day lily
nut grass (Cyperus rotundus)
Carex alopecuroides var. chlorostachya (species of sedge)
sedge
cotton grass (Eriophorum vaginatum subsp. fauriei)
sedge-woven (bamboo) hat
Phyllospadix iwatensis (species of seagrass)
lemon day-lily (Hemerocallis lilioasphodelus, formerly Hemerocallis flava); lemon lily; yellow day-lily
scoring combination consisting of the January and March 20-point cards and the February 10-point card
scoring combination consisting of the January, February and March 5-point cards